Composition for improved adhesion of vinylidene chloride latex to ionomer films

ABSTRACT

An adhesive composition, particularly useful for laminating carboxylate-containing films, comprises an aqueous dispersion of a film-forming vinylidene chloride copolymer wherein the vinylidene chloride copolymer includes on a comonomer weight basis: 
     (a) from about 45 to about 90 percent vinylidene chloride, 
     (b) from about 5 to about 25 percent of a polar comonomer having one or more hydroxyl groups, and 
     (c) from about 0 to about 30 percent of a plasticizing monomer for vinylidene chloride 
     in combination with: 
     (d) a cross-linking agent for hydroxyl groups selected from the group consisting of dialdehydes having between two and ten carbon atoms and compounds containing methylol groups dissolved in the continuous aqueous phase of the vinylidene chloride copolymer.

This application is a division of application Ser. No. 540,442, filedOct. 11, 1983, now U.S. Pat. No. 4,544,699.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The instant invention relates to water-based adhesive compositions, andmore particularly, to film-forming vinylidene chloridecopolymer-containing adhesives for use with polymer films, especiallyionomer films containing carboxylate functionalities neutralized bymetal ions. Such adhesives are especially useful as laminating adhesivesfor providing laminated constructions of ionomer carboxylate-containinghydrophobic films, especially carboxylated polyethylene films, whereinsaid constructions are characterized by low grease transmission and highhot tack provided by the ionomer films as well as low moisture vaportransmission and low oxygen transmission provided by the adhesivecoating.

2. Description of the Art

It is well known that hydrophobic films may be laminated with solventbased adhesive systems such as the one and two component urethaneadhesives and the solvent based vinylidene chloride copolymer adhesivesknown in the art. It is also well known that there are certaindifficulties attendant with the use of such solvent based systems. Forexample, at least a major portion of the solvent must be removed fromthe adhesive after application to form a functional adhesive layer,which in turn necessitates additional equipment to ensure that thesolvent does not enter the environment or affect persons applying theadhesive. Furthermore, although it is economically desirable to recoverthe solvent, even the best solvent recovery equipment operates with someloss of solvent.

Water based adhesives (or surfactant-stabilized dispersions of theadhesive in water) are more desirable since the removal of water fromthe applied adhesive does not encounter the difficulties associated withthe known solvent based systems. Nor is it economically necessary torecover the water. Water based adhesives, however, do not generallyprovide sufficient adhesion of hydrophobic films such as polyolefinfilms, and especially carboxylated polyolefin films such as Surlyn®film, either to other hydrophobic films or to non-hydrophobic films suchas polyester films, cellulose films, or nylon films. When water basedadhesives are used to laminate films, they must be formulated withminimum amounts of free surfactant to approach the adhesive propertiesof the solvent based systems. However, it has been generally found thatas the free surfactant concentration of the water based adhesives isdecreased, the stability also decreases. Decreased stability is aproblem in commercial operation since the adhesives must be applied athigh shear rates to maximize production. Such high shear rates are knownin the art to destabilize water based adhesives.

Vinylidene chloride copolymers have been used to formulate water basedadhesives for laminating various substrates to hydrophobic films. Ingeneral these adhesives are utilized to take advantage of the barrierproperties, i.e., low moisture vapor and oxygen transmission properties,provided by the vinylidene chloride portion of the copolymer. Therefore,vinylidene chloride copolymers having a high (i.e. up to 95 percent byweight) vinylidene chloride content have been generally used in suchwater based adhesives. For example, a series of patents to Dodwell andothers disclose vinylidene chloride copolymers having at least 60 molepercent vinylidene chloride, and preferably at least about 80 percent byweight vinylidene chloride, as useful for adhering a hydrophilic silverhalide emulsion to a hydrophobic polyester film. (See U.S. Pat. Nos.4,287,298; 4,244,988; and 4,233,074). These patents suggest that anadhesion promoter be utilized to assist in binding the vinylidenechloride adhesive to the hydrophobic polyester film. Therefore, the highamount of vinylidene chloride taught by Dodwell does not interfere withthe adhesive properties of the copolymer. See also U.S. Pat. Nos.3,988,157 and 4,002,802, to Van Paesschen et al. and Bayless et al.,respectively, for other examples of the use of vinylidene chloridecopolymers in photographic film.

Some patents disclose that copolymers having a high vinylidene chloridecontent tend to be crystalline and therefore special techniques arerequired for their use as adhesives or coatings. For example, in U.S.Pat. No. 3,922,451 to Anschutz et al., the vinylidene chloride copolymeris heated to a temperature of at least 110° C. to adhere the copolymerto the substrate. In U.S. Pat. No. 3,908,070 to Marzolf, the vinylidenechloride copolymer is externally plasticized and applied to films by acoextrusion technique in order to obtain the necessary adhesivecharacteristics.

Smith et al. in U.S. Pat. No. 3,850,726 teach the use of vinylidenechloride copolymers comprising 70 to 95 percent by weight vinylidenechloride to laminate a polyolefin film to another polyolefin. Again, dueto the nature of the vinylidene chloride copolymers disclosed therein,the adhesive must be heat sealed at a temperature of about 270° F. toobtain a substantial adhesive bond between the polyolefin films.

The vinylidene chloride copolymers described in the above referencesgenerally include the lower alkyl acrylate ester comonomers, such asmethyl, ethyl and butyl acrylate and methacrylate, in combination withrelatively high amounts of vinylidene chloride. The lower alkylacrylates somewhat increase the film-forming capability of thevinylidene chloride copolymer but do not contribute sufficientplasticizing action to yield copolymers flexible enough to be utilizedin laminating very flexible films, such as polyolefins, withoutdiminishing the low temperature flexibility of the polyolefin film. Morespecifically, the combination of high vinylidene chloride content andthe lower alkyl acrylate comonomers results in copolymers having a glasstransition temperature (Tg) greater than 0° C. (The Tg is thetemperature at which a polymer changes from the glassy state to anamorphous state.) Therefore at temperatures of about 0° C. and less, thepolyolefin film laminate may become stiff due to the above vinylidenechloride copolymer adhesives.

Vinylidene chloride copolymer compositions containing lower amounts ofvinylidene chloride (and a lower crystallinity) are taught by Balloni etal. in U.S. Pat. No. 4,144,363 as useful adhesives for polyolefin films.These compositions are solvent based adhesives and therefore subject tothe difficulties in use noted above.

Exceptional difficulties have been encountered in applying adhesives,including vinylidene chloride adhesives, to ionomer films such asSurlyn® film, a polyethylene film having attached carboxylic acidfunctionalities which are neutralized with metal ions, particularly zincand sodium. Ionomer films such as Surlyn® film are highly desired foruse by convertors because of their low cost, high hot tack andimpermeability to grease, but even vinylidene chloride copolymers, i.e.copolymers having a high ratio of acrylate to vinylidene chloridemonomer, suitable for bonding to both hydrophobic and nonhydrophobicsubstrates, do not adhere well to ionomer carboxylate-containingcopolymers such as Surlyn® film. Moreover, adhesives containingsufficiently high acrylate to vinylidene chloride ratios arecorrespondingly deficient in the moisture barrier properties of the highvinylidene chloride-containing adhesives. The metal ions on the surfaceof the ionomer films prevent wetting by the polyvinylidene chlorideadhesive and therefore impair adhesion thereto. Improved adhesion ofpolyvinylidene copolymers to films of ionomer carboxylate-containingcopolymers having attached metal ions requires a method of altering theadverse effect upon adhesion of the metal ions contained on the surfaceof the ionomer films.

Therefore, it is the primary object of this invention to provide afilm-forming water based adhesive composition suitable for laminatingionomer hydrophobic films containing carboxylate components neutralizedby metal ions.

It is another object of the invention to provide water basedfilm-forming vinylidene chloride copolymers suitable for use withhydrophobic polyethylene films containing carboxylate components whichdo not require heating above 250° F. to be useful adhesives.

It is another object of the invention to provide laminated structuresincluding one or more hydrophobic or non-hydrophobic films adhered to anionomer carboxylate-containing film and having substantial delaminationresistance at high humidity conditions.

A further object of the invention is to provide heat-sealed structuresof two or more ionomer carboxylate-containing polyethylene films.

It is another object of the invention to provide a process for adheringionomer carboxylate-containing polyethylene films to hydrophobic filmswith an aqueous vinylidene chloride copolymer adhesive.

Other objects, advantages and features of this invention will becomeapparent to those skilled in the art from the following description.

SUMMARY OF THE INVENTION

Briefly, this invention provides a film-forming adhesive compositionuseful in laminating substrates containing at least one ionomercarboxylate-containing hydrophobic film, said adhesive compositioncomprising a dispersion of a vinylidene chloride copolymer in water, thevinylidene chloride copolymer comprising on a comonomer weight basis:

(a) from about 45 to about 90 percent vinylidene chloride,

(b) from about 5 to about 25 percent of a polar comonomer having one ormore polar groups selected from the group consisting of allhydroxyl-containing components, and

(c) from about 0 to about 30 percent of a plasticizing monomer forvinylidene chloride

in combination with:

(d) a cross-linking agent for hydroxyl groups. Preferably thecross-linking agent for hydroxyl groups is chosen from the groupconsisting of dialdehydes having between two and ten carbon atoms, boricacid, water-soluble metal salts of boric acid, and compounds containingmethylol groups, such as urea formaldehyde resins andphenol-formaldehyde resins, or mixtures thereof.

Such adhesive compositions are useful for laminating hydrophobic filmsto non-hydrophobic films or to other hydrophobic films or substrates soas to provide laminated structures having good oxygen and moisture vaporbarrier properties. Such hydrophobic films may include polyolefin filmssuch as polyethylene, polypropylene, and ionomer carboxylate-containingpolyethylene films, especially Surlyn® film. Less hydrophobic films(which are characterized as non-hydrophobic films for the purpose ofthis invention) such as nylon, cellulose and polyester films may also belaminated or may be laminated to Surlyn® film with the above adhesivecompositions Such laminated structures containing Surlyn® film providehigh resistance to grease transmission and high hot tack characteristicsand may be used in packaging food products, apparel, medicines, oils,lotions and the like.

DETAILED DESCRIPTION OF THE INVENTION

The present invention is directed to compositions especially useful asadhesives, containing aqueous dispersions of a film-forming vinylidenechloride copolymer, wherein the copolymer is the reaction product ofvinylidene chloride, a hydroxyl-containing polar comonomer, and,optionally, a plasticizing comonomer and a copolymerizable sulfonic acidor salt, in combination with a cross-linking agent for hydroxyl groupsdissolved in the aqueous solution of said copolymer.

Dispersions of such polymers are useful as laminating adhesives,particularly with respect to bonding together hydrophobic film layers,and, in one embodiment, the invention is directed to laminatedstructures containing at least one substrate layer of an ionomerpolyethylene carboxylate-containing film secured with the adhesivecomposition of the invention.

The vinylidene chloride comonomer imparts film forming properties to theabove copolymer and in view of the chemical nature of vinylidenechloride provides a barrier for oxygen and moisture vapor. As notedabove, vinylidene chloride tends to form crystalline polymers which donot adhere well to substrates such as hydrophobic films, unless heatedto a high temperature, e.g., at least about 150° C.

This temperature is not economically reached by means of the filmcoating techniques and equipment in present day commercial use and inany event would destroy or distort many of the hydrophobic filmsdescribed herein. Usually, therefore, either a plasticizing comonomerfor vinylidene chloride or an external plasticizer is incorporated intothe vinylidene chloride copolymers useful in the adhesive compositionsof the invention. The crystalline nature of vinylidene chloride can bemodified by copolymerizing therewith one or more alkyl esters of acrylicacid or methacrylic acid wherein the alkyl group of said ester comprisesfrom one to ten carbon atoms. The acrylic acid and methacrylic acidesters are plasticizing comonomers for vinylidene chloride and may bedesignated as internal plasticizers. External plasticizers forvinylidene chloride, known in the art, are not copolymerized with thevinylidene chloride monomer. External plasticizers are relatively lowmolecular weight compounds which are soluble in the vinylidene chloridehomopolymer or copolymer and impart soft properties to the polymer. Theplasticizing comonomers increase the film forming tendencies ofvinylidene chloride copolymers and, may, in addition, increase theadhesion of the copolymers to hydrophobic surfaces. In particular, theabove esters of acrylic acid or methacrylic acid provide adequate filmforming properties at a temperature suitable for use by convertors usingthe techniques and equipment available in commercial practice.

For best results, the ester is selected from the group consisting ofacrylic acid esters rather than methacrylic acid esters, since acrylicacid esters tend to soften the copolymer more efficiently on an equalweight basis. More preferably, the ester is selected from the groupconsisting of methyl acrylate, n-butyl acrylate, n-hexyl acrylate, and2-ethyl hexyl acrylate, which provide the best balance of adhesiveproperties to the vinylidene chloride copolymer without a significantloss of oxygen and moisture vapor barrier properties.

The polar comonomer, through the included hydroxyl group, impartsincreased adhesiveness to the vinylidene copolymer adhesive compositionand provides a site, i.e. the hydroxyl group, for reaction with thecross-linking agent. Preferably the polar comonomer is selected from thegroup consisting of all components having one or more hydroxyl groups.More preferably, the polar comonomer is selected from the groupconsisting of 2-hydroxyethylacrylate, 2-hydroxypropylacrylate,2-hydroxyethylmethacrylate and 2-hydroxypropylmethacrylate. Mostpreferably, the polar comonomer is 2-hydroxyethylacrylate.

To provide the desired balance of adhesive and barrier properties, thevinylidene chloride copolymer comprises from about 45 to about 90percent, by weight, vinylidene chloride and from about 5 to about 25percent, by weight, of the polar comonomer. At more than 90 percent byweight of vinylidene chloride, the copolymers are too crystalline andthus do not provide adequate film forming and adhesive properties at thetemperatures in use in commercial operations. At levels of less thanabout 45 percent, by copolymer weight of vinylidene chloride, thebarrier properties are insufficient to provide laminated structureshaving good barrier properties, even with the above hydrophobic films.Therefore compositions having about 70 to 82 percent by copolymer weightof vinylidene chloride are most preferred as combining good barrierproperties with good film-forming and adhesive properties.

Preferably, the vinylidene chloride copolymer of the present inventionwill comprise from about 5 to about 25 percent, by weight, of the polarcomonomer. More preferably, the polar comonomer is from about 7 to about12 percent by weight of the copolymer. The most preferred concentrationof polar comonomer is about 10 percent by weight of the copolymer, atwhich concentration, the compositions of this invention provide the mosteffective bonding of the copolymer adhesive to ionomercarboxylate-containing films. A lower level of polar comonomer does notprovide sufficient chemical interaction with the cross-linking agent toreduce the adverse effect upon adhesion of the metal ions on the surfaceof ionomer films. A higher level of polar comonomer will inorease theviscosity of the dispersion of the vinylidene chloride copolymer of thisinvention to an unacceptably high level. When 2-hydroxyethylacrylate or2-hydroxypropylacrylate is utilized, up to 25 percent by weight may beincluded in vinylidene chloride copolymers and a dispersion having aviscosity suitable for application by the techniques and equipmentcommercially used in the coating of films is obtained. For example, at25° C., a composition comprising 45 percent by copolymer weight cf avinylidene chloride copolymer and about 10 percent2-hydroxyethylacrylate and the balance a plasticizing comonomertypically has a viscosity less than 200 cps.

Although the polar comonomer will also contribute to the flexibility ofthe copolymer, the copolymer optionally contains sufficient amounts of asuitable plasticizing agent to further increase flexibility at lowtemperatures. For example, an internal plasticizing agent such as theplasticizing comonomer 2-ethylhexyl acrylate may be included in saidcopolymer at a level of as low as 10 percent by weight to yield suitableflexible copolymers. If n-butyl acrylate is utilized as the plasticizingcomonomer, then higher proportions, e.g. about 25 percent or greater, byweight, may be necessary to provide copolymers having sufficientflexibility to provide laminated structures that are flexible at lowtemperatures. In copolymers utilizing high percentages of vinylidenechloride comonomer, for example about 90 percent of vinylidene chloride,external plasticizing agents are preferred to enhance film forming.

As discussed above, vinylidene chloride copolymer adhesives of the priorart generally contain a relatively high proportion of vinylidenechloride and a correspondingly lower proportion of the lower alkylacrylates such as methylacrylate to emphasize the chemical properties ofthe vinylidene chloride. These materials are substantially less flexiblethan polyolefin films at low temperatures but are utilized for the waterresistant properties of the vinylidene chloride comonomer. However, toobtain good adhesion with high vinylidene chloride copolymers,substantial heating is required. For example, heating to temperatures ofabout 260° F. and greater, i.e., from about 270° F. to 300° F., iscommon. In comparison, the instant copolymers in combination with thecross-linking agent are useful as laminating adhesives, i.e., at themuch lower temperatures in the range of from about 130° F. to about 250°F.

Thus, in the preferred embodiment of the invention, the proportion andidentity of the above comonomers are selected to provide flexiblecopolymers suitable for laminating flexible films such as polyolefins toprovide flexible laminated structures while providing sufficientvinylidene chloride to obtain the desired oxygen and moisture vaportransmission properties. The copolymer will have a sufficiently reducedcrystallinity to ensure low temperature flexibility of laminatescontaining the instant vinylidene chloride copolymer adhesives.

In addition to comonomers (a), (b) and (c), the vinylidene chloridecopolymers of the invention optionally will include a copolymerizablesulfonic acid or salt. The sulfonic acid or salt is usually selectedfrom the group consisting of sulfonic acids and their salts having theformulae: R--Z--Q--SO₃ ⁻ M⁺ and R--SO₃ ⁻ M⁺ wherein R is selected fromthe group consisting of vinyl and alpha substituted vinyl; Z representsa difunctional linking group which will activate the double bond in thevinyl group (e.g. a carboxylic group, a carboxy amido group, etc.);--Q-- is a divalent hydrocarbon having its valence bonds on differentcarbon atoms; and M⁺ represents a cation selected from the groupconsisting of hydrogen, ammonium, and alkali metal cations. Exemplary ofsuch materials are sodium vinylsulfonate, sodium 2-sulfoethylmethacrylate, 2-acrylamido-2-methylpropane sulfonic acid, and sodium2-hydroxy-3-sulfopropyl methacrylate.

The copolymerizable sulfonic acid or salt thereof stabilizes thedispersion of the vinylidene chloride copolymer adhesive. Thus, byincorporating from about 0.2 to about 1.5 parts of said copolymerizablesulfonic acid or salt per hundred parts of said vinylidene chloride,plasticizing comonomer and polar comonomer, the amount of freesurfactant necessary to provide a stable adhesive dispersion may bereduced to less than about 1 percent, by weight, dispersion, e.g., lessthan 0 5 percent, by weight, dispersion.

The above stabilizing monomers function as a surfactant (as well as anadhesive aid) but are not considered `free` surfactants because they arecopolymerized with the above comonomers (a), (b) and (c). Thus suchstabilizing monomers are not free to migrate and interfere with theadhesive properties of the vinylidene chloride copolymer. It isgenerally desirable to utilize as little free surfactant as possible toenable better adhesion to hydrophobic surfaces such as polyethylene,polypropylene, etc.

The preferred stabilizing monomer is selected from the group consistingof the alkali metal salts of 2-sulfoethylmethacrylate and vinylsulfonate. While vinylsulfonate and its salts are useful as acopolymerizable sulfonic acid or salt, it has been found that vinylsulfonate when made by the commercial process generally contains anexcess of sodium ion which may interfere with the adhesive bond strengthof the vinylidene chloride copolymer. Therefore, the most preferredstabilizing comonomer is selected from the group consisting of thealkali metal salts of 2-sulfoethylmethacrylate, e.g. sodium2-sulfoethylmethacrylate.

The composition of this invention comprises a film-forming aqueousdispersion of the above-described vinylidene chloride copolymers incombination with a cross-linking agent for hydroxyl groups dissolved inthe continuous aqueous phase of said copolymer. The cross-linking agentincludes compounds having at least two groups capable of reacting withthe hydroxyl group of the polar comonomer on each molecule ofcross-linking agent. Usually the composition contains from about 0.01 toabout 3 equivalents per equivalent of hydroxyl group contained in saidpolar comonomer of said cross-linking agent selected from the groupconsisting of dialdehydes containing from two to ten carbon atoms, boricacid, water-soluble metal salts of boric acid and compounds containingmethylol groups, such as urea formaldehyde resins, phenol formaldehyderesins, or mixtures thereof, and preferably selected from the groupconsisting of dialdehydes containing from two to ten carbon atoms, boricacid, water-soluble metal salts of boric acid, and particularly sodiumtetra borate. More preferably the composition contains from about 0.04to about 1.2 equivalents per equivalent of hydroxyl group contained insaid polar comonomer of said cross-linking agent selected from the groupconsisting of dialdehydes having two to six carbon atoms, includingglyoxal, malonaldehyde, succinaldehyde, glutaraldehyde, andadipaldehyde, boric acid, and water-soluble metal salts of boric acid,or mixtures thereof. Most preferably the composition contains from about0.07 to about 1.0 equivalents per equivalent of hydroxyl group containedin said polar comonomer of a cross-linking agent for hydroxyl groupschosen from the group consisting of glyoxal and sodium tetra borate,with sodium tetra borate most preferred. The improvement in adhesivenessto polyethylene ionomer carboxylate-containing films resulting fromusing the copolymer adhesive in combination with the cross-linking agentdoes not decrease the effectiveness of the film as an oxygen barrier.

When the salts of boric acid are employed as cross-linking agents,compositions containing more than about 2 equivalents per equivalent ofhydroxyl group contained in said polar comonomer of water-soluble metalsalts of boric acid usually display decreased adhesiveness due to thetendency of the salts to orient themselves at the surface of the film insuch a way as to interfere with wettability of the film. Also, theformaldehyde-containing cross-linking agents produce undesirable sideeffects. Urea formaldehyde and phenol formaldehyde resins are theleast-preferred of the cross-linking agents since they are the leasteffective for increasing adhesiveness to ionomer carboxylate containingfilms and possess the additional undesirable trait of releasing noxiousformaldehyde gas during the cross-linking reaction.

The most suitable composition for preparing laminates of hydrophobicfilms having an ionomer carboxylate-containing copolymer as at least oneof the substrates will preferably be a film-forming vinylidene chloridecopolymer including on a comonomer weight basis:

(a) from about 70 to about 82 percent vinylidene chloride

(b) from about 6 to about 23 percent of a plasticizing agent forvinylidene chloride chosen from the group consisting ofethylhexylacrylate and methyl, ethyl and butyl acrylates andmethacrylates and

(c) from about 7 to about 12 percent of a polar comonomer selected fromthe group consisting of 2-hydroxypropylacrylate, 2-hydroxyethylacrylate,2-hydroxypropylmethacrylate and 2-hydroxyethylmethacrylate

in combination with:

(d) from about 0.7 to about 1.0 equivalents per equivalent of hydroxylgroup contained in said polar comonomer of sodium borate dissolved inthe continuous aqueous phase of said copolymer.

The film-forming polyvinylidene chloride copolymer dispersions of theinstant invention may comprise from about 40 to about 50 percent, byweight, solids. It is generally desirable that as little water aspossible be utilized as the continuous or dispersing medium, to promoteease of drying. However, such dispersions tend to increase in viscosityas the solids content increases, and higher viscosities make applicationof the adhesive to film more difficult. Generally a solids content ofabout 45 percent, by weight, is suitable to balance ease of drying withlower viscosity.

The film-forming polyvinylidene chloride copolymer dispersions of theinstant invention generally will have an average particle size of fromabout 200 nm to about 450 nm, e.g., about 350 nm, and a fairly uniformparticle size distribution. A lower average particle size tends toincrease the viscosity of the dispersion (on an equal solids basis)while a higher average particle size may lead to poor film formationupon drying.

The film-forming polyvinylidene chloride copolymer dispersions of theinvention will generally have a surface tension of less than 60dynes/cm, and preferably less than 55 dynes/cm. The surface tensionvalues are easily achieved with the low amounts of free surfactantrequired to stabilize the polyvinylidene copolymer dispersions.Moreover, such surface tension values allow the polyvinylidene chloridecopolymer in combination with the cross-linking agent to more easily wetand adhere to hydrophobic polyolefin films such as polypropylene,especially to Surlyn® film.

The above described aqueous dispersion of the film-forming vinylidenechloride copolymer may be prepared by the emulsion polymerization ofvinylidene chloride copolymer with the above acrylate comonomers. Forexample, vinylidene chloride and the above described comonomers may beemulsified in water and copolymerized in the presence of a redoxcatalyst system or other polymerization catalyst.

In one polymerization procedure, the comonomers, in amounts suitable forpreparing the above vinylidene chloride copolymer, are emulsified in anaqueous solution comprising a small amount of one or more nonionicsurfactants and one or more anionic wetting agents. To this emulsion aportion of the oxidant used in the redox catalyst system is added andthe resulting solution buffered by addition of a suitable bufferingagent. The emulsion is then metered to a polymerization reactor andtherein combined (at a temperature effective to polymerize saidcomonomers) with an aqueous solution comprising the reductant of saidredox catalyst system and additional nonionic surfactant and/or anionicwetting agent. Additional oxidant may also be metered to saidpolymerization reactor to ensure complete polymerization of thecomonomers. Preferably the nonionic surfactant is selected from thegroup consisting of the ethylene and propylene oxide adducts of analkylphenol. The alkylphenol adducts may be represented by compoundshaving the general formula: ##STR1## wherein R₁ is selected from thegroup consisting of C₆ to C₁₂ alkyl radicals, preferably C₈ to C₁₀ alkylradicals, e.g., octyl and nonyl; R₂ is selected from the groupconsisting of hydrogen and methyl radicals, preferably hydrogenradicals; and n ranges from about 10 to about 40, preferably from about20 to about 30, e.g., about 30.

Preferably the anionic wetting agent is selected from the groupconsisting of alkali metal and ammonium salts of organic sulfonates andphosphates. For example, the alkali metal or ammonium salts of alkylaryl sulfonates such as sodium dodecyl benzenesulfonate, sodium diamylnaphthalene sulfonate, etc.; the alkali metal or ammonium salts of alkylsulfates such as sodium laurylsulfate, sodium myristyl sulfate, etc.;the alkali metal or ammonium salts of an alkyl phenoxy (polyethyleneoxy) ethyl ester of phosphoric acid, etc. The sodium salt ofdicyclohexylsulfosuccinate has been found to be especially suitable forpreparing the vinylidene chloride copolymers of the instant invention.

In a most preferred embodiment, a mixture of a nonionic surfactant suchas a 30 mole ethylene oxide adduct of nonyl phenol, with the sodium saltof dicyclohexylsulfosuccinate and an ammonium or sodium salt of analkylphenoxy (polyethylene oxy) ethyl ester of phosphoric acid is usedto emulsify the above monomer mixture and stabilize the resultingvinylidene chloride copolymer dispersion

The total amount of the nonionic surfactant and anionic wetting agentshould be less than about 1 percent, more preferably from about 0 05 toabout 0.4 percent, by weight of the dispersion This low amount of freesurfactant is suitable to stabilize the vinylidene chloride copolymerdispersion without significantly diminishing its adhesive properties.

The suitable buffering agent is used to prevent pH variations duringpolymerization which might interfere with the polymerization reaction.For example diammonium phosphate, diammonium citrate, etc. may be used.It has been found that for the purpose of preparing the vinylidenechloride copolymers of the instant invention dibasic ammonium citrate isespecially preferred as a buffering agent since its chelating naturehelps stabilize the resulting vinylidene chloride copolymer.

As is well known in the art, a redox catalyst system requires an oxidantand a reductant which, upon combination at a temperature suitable forpolymerization, react to yield free radicals. Suitable oxidants forpreparing the vinylidene chloride copolymers of the invention are theperoxides, hydroperoxides, aliphatic azo compounds and persulfates. Forexample hydrogen peroxide, benzoyl peroxide, tertiary butylhydroperoxide, azodisobutyronitrile, and ammonium persulfate aresuitable. A mixture of hydrogen peroxide and ammonium persulfate hasbeen found to be especially preferred for preparing the copolymers ofthe instant invention.

The reductant may be selected from the group consisting of inorganicreductants, such as sulfites, bisulfites, ferrous salts, etc. andorganic reductants such as erythorbic acid, ascorbic acid, sulfoxylates,such as zinc or sodium formaldehyde sulfoxalate. Erythorbic acid is anespecially preferred reductant for preparing the vinylidene chloridecopolymers of the invention.

The polymerization is carried out at a temperature sufficient todecompose the redox catalyst to form free radicals. For example, apolymerization temperature of at least 100° F., more preferrably 120° to130° F., is preferred

The polymerization reaction is preferably effected at a polymerizationtemperature for a time sufficient to copolymerize substantially all ofthe above monomers Usually, time periods of about 30 minutes to about 2hours or more are required.

The polymerization reaction should be carried out in a glass-linedvessel or a high quality stainless steel vessel. Suitable equipment forcopolymerizing vinylidene chloride is well known in the art and need notbe described further herein.

The aqueous film-forming vinylidene chloride copolymer dispersion of thepresent invention may be formulated with various additives known in theart to impart special properties to water based adhesives. For example,if desired, film-forming aids such as low molecular weight externalplasticizers (both volatile, i.e., "fugitive," and non-volatile) may beadded to further improve film forming properties. However, as notedabove, the vinylidene copolymer of the instant invention having lessthan about 90 weight percent vinylidene chloride copolymer hasespecially good adhesive properties without the addition of externalplasticizers.

If desired, antioxidants such as tertiary-butyl hydroxy toluene,2-hydrobenzophenones, aryl substituted acrylates, substitutedbenzotriazoles, etc., may be formulated with the vinylidene chloridecopolymer to further enhance the otherwise good oxidation resistance ofthe copolymer.

Fillers and other inert materials are sometimes combined with adhesivesby the convertor to provide desired properties. Any of the known inertmaterials such as clays, calcium carbonate, etc. may be combined withthe vinylidene chloride adhesive composition without detriment.

The adhesive compositions of this invention are made by thoroughlymixing a cross-linking agent for hydroxyl groups or an aqueous solutionof said cross-linking agent, such as 5 percent by weight aqueoussolution of the chosen cross-linking agents for hydroxyl groups, intothe continuous aqueous phase of the vinylidene chloride copolymerdispersion after the polymerization reaction has been completed.

The adhesive compositions of the invention, containing a vinylidenechloride copolymer in combination with the cross-linking agent forhydroxyl groups may be applied by the various techniques known in theart for the application of adhesives. For example, the copolymer may beapplied by kiss-roll techniques, grauvere roll techniques, etc.

In general the above adhesive compositions are useful as laminatingadhesives for both hydrophobic and non-hydrophobic substrates,especially films. For the purpose of the instant invention, the termhydrophobic film shall refer to films having a surface tension similarto (or less than) the polyolefins such as polypropylene. (The surfacetension of polypropylene is about 29 dynes/cm )

Typical non-hydrophobic films may include nylon, for example, filmsprepared f rom nylon polymers such as nylon-4, nylon-6, nylon-12, andnylon-66. Note that nylon is defined for the purposes of this inventionas any long chain synthetic polymer which has recurring amide groups asan integral part of the polymer chain.

Another class of non-hydrophobic films which may be converted intolaminated structures by the aqueous adhesives of the instant inventionincludes polyester films which may be prepared by the polyesterificationof a dicarboxylic acid and a dihydric alcohol. For example, thepolymerization of ethylene terephthalic acid or dimethyl terephthalatewith propylene glycol, diethylene glycol, tetramethylene glycol orcyclohexane 1,4 dimethyl provides polymers useful as polyester films.

The instant film-forming aqueous adhesives in combination with across-linking agent for adjacent hydroxyl groups are most useful forlaminating either hydrophobic or non-hydrophobic films to an ionomercarboxylate-containing hydrophobic film. Ionomer films are a class ofpolyolefins having pendant carboxylate groups associated with monovalentor divalent metal cations. In particular, Surlyn® film is an ionomerpolyolefin having about 90 weight percent polyethylene and about 10weight percent methacrylic acid neutralized by either zinc or sodiumions. Ethylene-carboxylic acid copolymers and the salts thereof, havingfrom about 0.5 to about 10 percent by weight of the carboxylic acid orsalt comonomer, are also useful in preparing the laminated constructionsof the instant invention.

Particular hydrophobic films which are useful in forming the laminatedstructures of the instant invention are the polyolefin films.Polyolefins include polyethylene and propylene and various copolymersthereof. For example, polyethylene films may include alcohol groups suchas the hydrolyzed copolymers of ethylene and vinyl acetate. In addition,propylene may be copolymerized with ethylene, to provideethylene-propylene copolymer film. Furthermore, terpolymers of ethylene,propylene and another comonomer such as a conjugated or non-conjugateddiene provide useful hydrophobic polyolefin films. Copolymers ofethylene and acrylate esters are also useful as films. For example,ethylene-ethylacrylate copolymers having from about 20 to about 30weight percent ethylacrylate and copolymers of ethylene and isobutylacrylate having from about 20 to about 30 weight percent isobutylacrylate provide films useful in preparing the laminated structure ofthe instant invention. Also, ethylene may be copolymerized withchlorinated monomers, such as vinyl chloride and vinylidene chloride, toprovide ethylene-vinylchloride copolymer films and ethylene-vinylidenechloride copolymer films, respectively. Such films may advantageouslycontain from about 5 to about 40 percent chlorine.

The polyvinylidene chloride copolymer adhesive of the instant inventionmay be applied to hydrophobic or non-hydrophobic films at a coatingweight of from about 1 to about 3 pounds per ream. One or more of thehydrophobic or non-hydrophobic films may be adhered to an ionomercarboxylate-containing film by forcefully engaging the ionomercarboxylate-containing film with a hydrophobic or non-hydrophobic filmcoated with the vinylidene chloride copolymer adhesive of the inventionunder heat and pressure conditions sufficient to cause the ionomer filmto adhere to the coated hydrophobic film. Techniques known in the artfor other adhesives may be employed, with nip roll being illustrative.

The adhesive of this invention may also be used to produce structureswhich laminate combinations of any of the above films. Especially usefulstructures are obtained by combining one or more of any of the abovepolyolefin films with nylon. For example, polyolefin films haveexcellent moisture vapor barrier properties but poor oxygen barrierproperties. Nylon films on the other hand show good oxygen barrierproperties but poor resistance to the passage of moisture vapor. Whensuch nylon and polyolefin are combined by adhesion through the abovevinylidene chloride copolymers, a composite structure is obtained whichhas both good oxygen barrier properties and moisture vapor transmissionproperties. The vinylidene chloride copolymer in combination with thecross-linking agent for adjacent hydroxyl groups does not detract fromthe barrier properties of the polyolefin and nylon films describedabove, and in addition contributes to such barrier properties. Thisparticular structure has been found to be extremely useful in packagingfoodstuffs, especially butter, soft cheese, margarine, fresh meat andthe like which are sensitive to water vapor and/or oxygen. Furthermore,the structures are useful in packaging beverages, meat products, fruits,vegetables, nuts, drugs or medicines, oils, or lotions and the like,which require protection from odors, moisture vapor, and/or oxygen.

In addition, combining one or more of any of the above polyolefin filmswith polyethylene carboxylate-containing films, especially Surlyn® film,provides structures with high grease resistance and excellent moisturebarrier properties since Surlyn® film is well known for its resistanceto penetration by grease and polyolefin films are noted for moisturevapor transmission properties. This structure has been found useful inpackaging potato chips, cheese, meat products, and the like whichrequire protection against grease transmission.

The invention is further illustrated by the following examples which areillustrative of specific modes of practicing the invention and are notintended as limiting the scope of the appended claims.

EXAMPLE 1

A most preferred polymerization procedure for preparing the vinylidenecopolymer dispersion of the instant invention is exemplified by thefollowing:

0.13 parts H₂ O₂, 0.16 parts of a 30 mole ethylene oxide adduct of nonylphenol, 0.04 parts of sodium dicyclohexylsulfosuccinate, 0.07 dibasicammonium citrate, and 0.05 parts ammonium persulfate are dissolved in21.91 parts by weight water and charged to a glass lined reactor. Twopercent, by weight, of a `pre-emulsion` prepared by emulsifying 8.98parts 2-ethylhexylacrylate, 4.55 parts of 2-hydroxyethylacrylate and31.46 parts vinylidene chloride, in a solution comprising 17.3 partswater, 0.06 parts of the above ethylene oxide adduct of nonylphenol,0.14 parts sodium dicyclohexylsulfosuccinate, 0.10 parts of an alkyl(phenoxy polyethylene oxy) ethyl monoester of phosphoric acid that hasbeen neutralized with ammonium hydroxide to a pH of 6.5 (Gafac RE-960,available from GAF), and 0.45 parts of a 50 percent aqueous solution of2-sulfoethylmethacrylate that has been neutralized with sodium hydroxideto a pH of 5.0 is also charged to the reactor. The reactor charge isheated to 125° F. while agitating and the remainder of the`pre-emulsion` and a solution comprising 0.1 parts erythorbic acid in9.4 parts water along with a solution of 0.12 parts H₂ O₂ in 3.3 partswater are concurrently added to the reactor over a period of time tocopolymerize substantially all of the above monomers. Heating iscontinued after cessation of the concurrent addition and then thepolymerized mixture is allowed to cool to room temperature. Thecopolymer prepared by this most preferred polymerization procedure isdesignated as Sample A in the following examples. The composition ofthis invention is prepared by stirring a 5 percent by weight of aqueoussolution of sodium tetra borate into three samples of the continuousaqueous phase of the copolymer until it is dissolved. The amount ofsodium tetra borate in the samples identified as A through D varies fromzero to 5 percent by weight.

EXAMPLE 2

Dispersions of vinylidene chloride copolymers in water are prepared inaccordance with the most preferred polymerization procedure utilizingthe oxidant, reductant, surfactant mixture and buffering agent disclosedtherein, with the relative proportions of the comonomers being adjustedto provide the copolymers identified as samples E through K in Table I.The copolymers are tested for adhesive characteristics by a test methodwhich comprises coating the dispersions of Table I on an orientedpolypropylene film, Mobil 410 B available from Mobil Chemical Company,by using a number 12 wire wound rod and drying the coated films at 120°C. for 30 seconds in an air circulating oven. The dried films arelaminated to a second film of Surlyn® F 1605 available from DuPontCompany (uncoated) using a Sentinel heat sealer at 170° F., 40 p.s.i.g.,and a one second dwell time and conditioned, prior to testing, by aging15 minutes, overnight at ambient conditions, or one week at ambientconditions. The conditioned films are cut into one-inch wide strips andsuch strips are T-peeled on a portable slip-laminate tensile tester,available from R. J. Harvey Instrument Co. of Hillsdale, New Jersey(hereinafter the "Harvey Tensile Tester") at a rate of 12 inches perminute. Where a range of values is given for the adhesion, the readingon the Harvey Tensile Tester is erratic, due to failure of the adhesiveby a zippering mechanism. Such `zippering` indicates a strong adhesivebond has been obtained. The upper value of such range indicates themaximum strength of the adhesive bond obtained.

It will be noted from the results reported in Table I that Samples C andD, each of which contains a copolymer comprising 70 weight percent ofvinylidene chloride, 20 weight percent of 2-ethylhexylacrylate, and 10percent of 2-hydroxyethyl acrylate in combination with 1.0 and 2.5weight percent of sodium borate, respectively, show the best adhesion,especially after aging overnight at ambient temperature.

It will also be noted that vinylidene chloride copolymers which containno sodium borate dissolved in the continuous aqueous phase, are notsuitable for adhesion to Surlyn® films, as is evidenced by the resultsof Samples A, E and J.

                                      TABLE I                                     __________________________________________________________________________                  Sample                                                                        A B  C  D  E F    G    H    I  J K                              __________________________________________________________________________    Weight % Comonomer.sup.(a)                                                    Vinylidene Chloride                                                                         70                                                                               70                                                                               70                                                                               70                                                                              50                                                                              50   50    60   50                                                                              82                                                                               82                            2-Ethylhexylacrylate                                                                        20                                                                               20                                                                               20                                                                               20                                                                              40                                                                              40   40    30   40                                                                              --                                                                              --                             Hydroxyethylacrylate                                                                        10                                                                               10                                                                               10                                                                               10                                                                              10                                                                              10   10    10   10                                                                              10                                                                               10                            Methylacrylate                                                                              --                                                                              -- -- -- --                                                                              --   --   --   -- --                                                                               8                             Sodium Borate --                                                                               1 2.5                                                                               5 --                                                                               5   2.5   1    1 --                                                                               5                             Adhesion/gms/inch                                                             Mobil 410B-Surlyn.sup.R F 1605                                                15 mins        0                                                                              165                                                                              300                                                                              380                                                                              25                                                                              100-250                                                                            150-325                                                                            125-350                                                                            380                                                                               0                                                                              400                            Overnight      0                                                                              400                                                                              400                                                                              400                                                                              10                                                                              100-275                                                                            150-350                                                                            400  400                                                                               0                                                                              275                            One Week      --                                                                              525                                                                              450                                                                              395                                                                              --                                                                              100-295                                                                            150-375                                                                            --   -- --                                                                              285                            __________________________________________________________________________     .sup.(a) Each sample includes 1 part sodium 2sulfoethylmethacrylate (SEM)     per 100 parts vinylidene chloride and acrylate monomers other than SEM.  

EXAMPLE 3

Sample C is utilized to laminate oriented polypropylene film, availablefrom Mobil, to Surlyn® film, available from DuPont. The orientedpolypropylene film is coated with sample C to a coating weight of 1.8pounds per ream. The coated polypropylene film film is dried by passingthrough an oven maintained at a temperature of 283° F. The dried filmand the uncoated Surlyn® film are laminated to each other by passingthrough a nip roll maintained at a temperature of 170° F. The line speedof the laminated film is about 200 feet per minute. The initial offmachine adhesive bond is measured at 300 g/in. using an Instron TensileTester with a jaw separation of one inch and a crosshead speed of twoinches per minute. It is found that the addition of 1 to 5 percent, bycopolymer weight of sodium tetra borate to Sample A improves thewettability of the polyolefin film and enables one to preparesuccessfully laminated Surlyn® film constructions directly off themachine. Such constructions, when tested for adhesive bond directly offthe machine, cannot be pulled apart without rupture of the film.

While particular embodiments of the invention have been described, itwill be understood, of course, that the invention is not limited theretosince many obvious modifications can be made, and it is intended toinclude within this invention any such modification as will fall withinthe scope of the appended claims.

Having now described the invention, I claim:
 1. An aqueous dispersion ofa film-forming vinylidene chloride copolymer comprising on a comonomerweight basis:(a) from about 45 to about 90 percent vinylidene chloride,(b) from about 5 to about 25 percent of a polar comonomer having one ormore hydroxyl groups, and (c) a cross-linking agent for said hydroxylgroups selected from the group consisting of dialdehydes having betweentwo and ten carbon atoms dissolved in the aqueous dispersion of thevinylidene chloride copolymer.
 2. The dispersion of claim 1 wherein saidcross-linking agent is glyoxal.
 3. The dispersion of claim 1 furthercomprising from about 0.2 to about 1.5 parts of a copolymerizablesulfonic acid or salt per 100 parts of comonomers (a), (b) and (c). 4.The dispersion of claim 3 wherein said copolymerizable sulfonic acid orsalt is selected from the group consisting of compounds represented bythe general formulae: R--Z--Q--SO₃ ⁻ M⁺ and R--SO₃ ⁻ M⁺ wherein R isselected from the group consisting of vinyl and alpha substituted vinyl,Z is a bifunctional linking group capable of activating the double bondin the vinyl group, Q is a divalent hydrocarbon having its valence bondson different carbon atoms, and M⁺ is a cation selected from the groupconsisting of hydrogen, ammonium, and alkali metal cations.
 5. Thedispersion of claim 4 further comprising from about 0.1 to about 30percent of a plasticizing comonomer for vinylidene chloride selectedfrom the group consisting of alkyl esters of acrylic acid or methacrylicacid wherein the alkyl group comprises from 1 to 10 carbon atoms.
 6. Afilm-forming aqueous dispersion of a vinylidene chloride copolymercomprising on a comonomer weight basis:(a) from about 70 to about 82percent vinylidene chloride, (b) from about 7 to about 12 percent of apolar comonomer having one or more hydroxyl groups, (c) from about 5 toabout 23 percent of a plasticizing comonomer for vinylidene chloride,and (d) from about 0.07 to about 1.0 equivalents per equivalent ofhydroxyl group contained in said polar comonomer of a cross-linkingagent for said hydroxyl groups selected from the group consisting ofdialdehydes having between two and ten carbon atoms dissolved in theaqueous dispersion of the vinylidene chloride copolymer.
 7. Thedispersion of claim 6 wherein said cross-linking agent is glyoxal. 8.The dispersion of claim 6 further comprising from about 0.2 to about 1.5parts of a copolymerizable sulfonic acid or salt per 100 parts ofcomponents (a), (b) and (c).
 9. The dispersion of claim 8 wherein saidcopolymerizable sulfonic acid or salt is selected from the groupconsisting of compounds represented by the general formulae:R--Z--Q--SO₃ ⁻ M⁺ and R--SO₃ ⁻ M⁺ wherein R is selected from the groupconsisting of vinyl and alpha substituted vinyl, Z is a bifunctionallinking group capable of activating the double bond in the vinyl group,Q is a divalent hydrocarbon having its valence bonds on different carbonatoms, and M⁺ is a cation selected from the group consisting ofhydrogen, ammonium, and alkali metal cations.
 10. The dispersion ofclaim 9 wherein said plasticizing comonomer for vinylidene chloride isselected from the group consisting of methyl acrylate, n-butyl acrylate,n-hexyl acrylate, and 2-ethylhexyl acrylate
 11. The dispersion of claim9 wherein said polar comonomer is selected from the group consisting of2-hydroxyethyl acrylate and 2-hydroxypropyl acrylate.
 12. The dispersionof claim 9 wherein said sulfonic acid or salt comprises2-sulfoethylmethacrylate.
 13. The dispersion of claim 9 furthercomprising from about 0.05 to about 0.4 percent by weight freesurfactant.
 14. The dispersion of claim 13 wherein said free surfactantcomprises one or more nonionic surfactants and one or more anionicsurfactants.
 15. The dispersion of claim 14 wherein said nonionicsurfactant is selected from the group consisting of the ethylene andpropylene oxide adducts of alkyl phenols.
 16. The dispersion of claim 14wherein said anionic surfactant is selected from the group consisting ofthe alkali metal or ammonium salts of organic sulfonates and organicphosphate.
 17. A dispersion of a film-forming vinylidene chloridecopolymer comprising on a comonomer weight basis:(a) from about 70 toabout 82 percent vinylidene chloride, (b) from about 7 to about 12percent of a polar comonomer selected from the group consisting of2-hydroxyethylacrylate and 2-hydroxypropylacrylate, (c) from about 6 toabout 23 percent of a plasticizing agent for vinylidene chlorideselected from the group consisting of ethylhexylacrylate and methyl,ethyl and butyl acrylates and methacrylates, and (d) from about 0.07 toabout 1.0 equivalents per equivalent of hydroxyl group container in saidpolar comonomer of a cross-linking agent for hydroxyl groups selectedfrom the group consisting of dialdehydes having between two and 10carbon atoms.
 18. The dispersion of claim 8 wherein said plasticizingcomonomer comprises on a copolymer weight basis from about 9 to about 11percent and is chosen from the group consisting of 2-ethylhexylacrylate,butylacrylate and methylacrylate.
 19. The dispersion of claim 17 whereinsaid cross-linking agent is glyoxal.
 20. An adhesive compositioncomprising a vinylidene chloride copolymer, said copolymer comprising ona comonomer weight basis:(a) from about 45 to about 90 percentvinylidene chloride, (b) from about 5 to about 25 percent of a polarcomonomer having one or more hydroxyl groups, and (c) from about 0.1 toabout 30 percent of a plasticizing comonomer for vinylidene chloridereacted to cross-link with: (d) a cross-linking agent for said hydroxylgroups selected from the group consisting of dialdehydes having betweentwo and ten carbon atoms.
 21. An adhesive composition comprising thereaction product of:(a) a vinylidene chloride copolymer comprising:(1)from about 45 to about 90 percent vinylidene chloride, (2) from about 5to about 25 percent of a polar comonomer having one or more hydroxylgroups, (3) from about 0.1 to about 30 percent of a plasticizingcomonomer for vinylidene chloride, and (b) a cross-linking agent forhydroxyl groups from the group consisting of dialdehydes having betweentwo and ten carbon atoms.
 22. An aqueous dispersion as defined in claim1 which further comprises from about 0.1 to about 30 percent of aplasticizing comonomer for vinylidene chloride dissolved in the aqueousdispersion of the vinylidene chloride copolymer.
 23. An aqueousdispersion as defined in claim 2 which further comprises from about 0.1to about 30 percent of a plasticizing comonomer for vinylidene chloridedissolved in the aqueous dispersion of the vinylidene chloridecopolymer.
 24. An aqueous dispersion as defined in claim 3 which furthercomprises from about 0.1 to about 30 percent of a plasticizing comonomerfor vinylidene chloride dissolved in the aqueous dispersion of thevinylidene chloride copolymer.
 25. The dispersion of claim 16 whereinsaid nonionic surfactant is selected from the group consisting ofcompounds having the general formula: ##STR2## wherein R₁ is selectedfrom the group consisting of C₈ to C₁₀ alkyl radicals, R₂ is a hydrogenradical, and n ranges from about 20 to about 40; and said anionicsurfactant comprises a mixture of sodium dicyclohexylsulfosuccinate andan ammonium neutralized alkylphenoxy (polyethyleneoxy) ethyl phosphate.26. The dispersion of claims 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13,14, 17, or 18 wherein said hydroxyl groups are reactive to crosslinkwith said cross-linking agent at a temperature between about 130° to250° F.